Master cylinder assembly and reservoir for same

ABSTRACT

A master cylinder assembly combines a cast body with a stamped primary reservoir chamber. The primary reservoir is a single chamber which feeds fluids to two secondary reservoir chambers located in the master cylinder body. The fluids in the two secondary chambers are fed through appropriate compensating ports into the bore of the dual pressurizing chamber master cylinder. The master cylinder pistons function in the conventional manner to pressurize wheel brakes. The stamped reservoir is attached to the molded master cylinder body by shouldered tubular members which thread into the secondary reservoir chambers. One of the members which secures the primary reservoir body to the master cylinder body is a tubular member having an externally threaded section below the shoulder thereof which is threaded into the upper portion of one of the secondary reservoir chambers. It also has a centrally apertured head section which is of greater diameter than the externally threaded section so as to provide the shoulder therebetween which tightly holds the primary reservoir chamber bottom against the master cylinder body. A baffle plate is installed in the tubular member immediately adjacent the apertured head section. The baffle plate has a plurality of apertures adjacent its outer periphery and a solid center section which is in axial alignment with the cental aperture of the head section. This arrangement provides a tortuous fluid flow path between the compensation port of the associated secondary fluid reservoir chamber and the primary reservoir chamber, thereby preventing a squirt-like return of fluid from the associated fluid pressurizing chamber of the master cylinder directly into the primary fluid reservoir upon brake release.

United States Patent 1 Shellhouse 1 1 Apr. 15, 1975 1 1 MASTER CYLINDERASSEMBLY AND RESERVOIR FOR SAME [75] Inventor: Ronald L. Shellhause [73]Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Apr. 19, I974 [21] Appl. No.: 462,335

[52] US. Cl 60/585; 60/562 [51] Int. Cl. FlSb 7/08 [58] Field of Search60/562, 535, 585. 588

[56] References Cited UNITED STATES PATENTS 3.147596 9/1964 Wallace60/562 3.194019 7/1965 Lepelletier 60/562 X 3.470.695 10/1969 Kilb60/562 X FOREIGN PATENTS OR APPLICATIONS 872.272 7/1961 United Kingdom60/588 Primary E.\'aminerMartin P. Schwadron Assistant Examiner-H.Burks, Sr. Attorney, Agent, or FirmD. D. McGraw [57] ABSTRACT A mastercylinder assembly combines a cast body with a stamped primary reservoirchamber. The primary reservoir is a single chamber which feeds fluids totwo secondary reservoir chambers located in the master cylinder body.The fluids in the two secondary chambers are fed through appropriatecompensating ports into the bore of the dual pressurizing chamber mastercylinder. The master cylinder pistons function in the conventionalmanner to pressurize wheel brakes. The stamped reservoir is attached tothe molded master cylinder body by shouldered tubular members whichthread into the secondary reservoir chambers. One of the members whichsecures the primary reservoir body to the master cylinder body is atubular member having an externally threaded section below the shoulderthereof which is threaded into the upper portion of one of the secondaryreservoir chambers. It also has a centrally apertured head section whichis of greater diameter than the externally threaded section so as toprovide the shoulder therebetween which tightly holds the primaryreservoir chamber bottom against the master cylinder body. A baffleplate is installed in the tubular member immediately adjacent theapertured head section. The baffle plate has a plurality of aperturesadjacent its outer periphery and a solid center section which is inaxial alignment with the cental aperture of the head section. Thisarrangement provides a tortuous fluid flow path between the compensationport of the associated secondary fluid reservoir chamber and the primaryreservoir chamber, thereby preventing a squirt-like return of fluid fromthe associated fluid pressurizing chamber of the master cylinderdirectly into the primary fluid reservoir upon brake release.

2 Claims, 2 Drawing Figures MASTER CYLINDER ASSEMBLY AND RESERVOIR FORSAME The invention relates to a master cylinder of the type utilized ina hydraulic fluid brake system. and more particularly to one having aseparate master cylinder body and primary reservoir body. It is anobject of the invention to provide means securing the primary reser'voir body to the master cylinder body utilizing a shouldered tubularmember which provides additional structure improving the functionalrelationship of the reservoir chambers.

The invention is an improvement on the invention disclosed and claimedin US. patent application Ser. No. 408.461. filed Oct. 23. 1973.entitled Master Cylinder. That patent application discloses a stampedsteel primary reservoir chamber and a molded iron master cylinder body.the primary reservoir being a single chamber which feeds fluid to thetwo secondary reservoir chambers located in the master cylinder body. Asingle fluid level sensor is located in the primary chamber. The fluidsin the two secondary chambers supply each of the two tandem mastercylinder pressurizing chambers so that a loss of fluid in the primaryreservoir does not result in a loss of reservoir fluid for both mastercylinder pressurizing chambers.

It is an object of the invention to provide a headed tubular memberwhich extends through an aperture in the bottom of the primary reservoirbody and is threaded into the open end of a secondary reservoir chamberso as to fasten the primary reservoir body to the master cylinder body.the member also providing a baffle arrangement between the primaryreservoir chamber and the secondary reservoir chamber which establishesa continuous but tortuous fluid flow path between the primary reservoirchamber and the compensation port located at the bottom of the secondaryreservoir chamber and communicating with the master cylinder bore.

IN THE DRAWINGS FIG. 1 illustrates a master cylinder assembly with partsbroken away and in section. the assembly embodying the invention.

FIG. 2 is an end view of the master cylinder assembly of FIG. 1. takenin the direction of arrows 2-2 of that FIGURE. and having parts brokenaway and in section.

The master cylinder assembly includes a master cylinder body 12 and aprimary reservoir body 14. The

master cylinder body is preferably a permanent mold iron housing. butmay be made of other materials and by other processes while embodyingthe invention. A bore 16 is provided in the body 12 and pressurizingpistons l8 and 20 are reciprocably mounted in the bore. A piston stop 22cooperates with the rear end of piston 20 and the piston return springs24 and 26 to define the release position of the pistons. that positionbeing shown in the drawing. The pistons cooperate with the bore 16 todefine first and second pressurizing chambers 28 and 30. Outlets 32 and34 are respectively connected to different brake fluid circuits in avehicle brake system.- all in amanner well known in the art.

The upper portion of the master cylinder body 12 is formed to providesecondary fluid reservoir chambers 36 and 38. The chambers are definedin part by their respective side walls 40 and 42 and their bottoms 44and 46. These walls are integral parts of the cylinder 5 50 and 52 arerespectively provided to assure a fluid seal in each of these areas. Thecompensating ports 54 and 56. and the compensating ports 58 and 60.respectively provided through the secondary chamber bottoms 44 and 46.connect the secondary reservoir chamlt) bers with the bore l6. Ports 54and 58 respectively communicate with the pressurizing chambers 28 andwhen the master cylinder is in the release position shown. As is commonin the art. these ports are closed by the piston seals or cups 62 and 64when the pistons l5 l8 and 20 are moved in a pressurizing direction bymovement of the push rod 66. and are uncovered as the pistons return tothe release position and are positioned by stop 22. The compensationports are positioned in the bottoms of their respective secondaryreservoir 30 chambers well away from the chamber side walls 40 and 42.

The bottom 48 of the reservoir body I4 is provided with apertures 68 and70 which fit over the open ends of the secondary reservoir chambers 36and 38. At

least the upper portions of the chamber side walls and 42 haveinternally threaded sections 72 and 74. respectively. and apertures 68and are of a sufficient diameter to permit the insertion of threadedfastening members 76 and 78 so that they cooperate with the 30 threadedsections 72 and 74 to, tightly fasten the reservoir body 14 to themaster cylinder body 12. Member 76 and 78 are formed as shoulderedtubular members with externally threaded lower ends 80 and 82.respectively. the large diameter upper ends 84 and 86. respectively.This arrangement provides a shoulder 88 as a part of member 76 and ashoulder 90 as a part of member 78. These shoulders tightly engagereservoir bottom 48 when the members are threaded tightly into chambers36 and 38.

The upper end 86 of member 78 extends generally vertically abovereservoir bottom 48 into the primary reservoir section 92 and provides adam which prevents fluid in chamber 38 from flowing out of that chamberand into the primary reservoir section when the fluid level is theprimary reservoir section 92 falls below the lowest portion of the damupper edge. Therefore member 78 provides an extension of chamber 38 intothe primary reservoir section 92. The upper section 86 is a standpipesection and may be so shaped as to receive a suitable tool which can beused to thread member 78 into position during installation or to removemember 78 if needed. The removable seal cover 94 of the body 14 is notplaced into position during assembly until members 76 and 78 have beenthreaded into their fastening positions. Likewise. cover 94 is removedto permit access of tools to remove the fastening members. The upper end86 of member 78 is illustrated as being hexagonal to accept a similarlyshaped hexagonal tool. Other suitable arrangements may be made for theaccommodation of appropriate tools.

Fastening member 78 and its cooperative arrangement in the mastercylinder assembly is the subject of patent application Ser. No. 462.355.entitled Master Cylinder Assembly and Reservoir For Same". filed on thesame date herewith in the names of Duane H. Harwick and Dwight W.McDaniel as inventors and assigned to the common assignee.

Member 76 has its upper end 84 formed as a head having a shoulder 88 onits lower side. The head section formed by upper end 84 is provided witha central aperture 96. the generally annular portion 98 surroundingaperture 96 extending inwardly so that it covers a substantial outerperipheral area of the open end of chamber 36. Aperture 96 is formedwith circumferentially spaced and axially extending tabs 100 whichextend into chamber 36 from the annular portion 98. The tabs may bearranged to provide chord-like aperture surfaces of a generallypolygonal arrangement to receive a tool for threading member 76 into andout of chamber 36. Such a tool may be similar to the well known Allenwrench. for example. Also. the spaces 102 between adjacent tabs 100permit fluid flow through the aperture 96 and past tabs l in a generallyradial direction.

A baffle plate 104 is received in the upper portion of chamber 36 and inthe lower end 80 of member 76. The baffle plate 104 is preferablycastellated on its outer periphery to provide spring fingers or tabs 106which grip the inner wall of member 76 and hold the baffle plate againstthe ends oftabs 100. The baffle plate has a solid center portion 108which covers the inner end of aperture 96 so that any fluid passingthrough the aperture 96 must flow through spaces 102. The fluid can alsoflow past the spaces separating tabs 106. These latter spaces arepreferably positioned radially outwardly of chamber 36 relative to thecompensation ports 54 and 56. This arrangement provides a tortuous fluidflow path between the compensation ports and the primary reservoirsection 92. As noted in the earlier filed patent application referred toabove. this arrangement prevents unduc transfer of fluid from thesecondary reservoir chamber 36 to the primary reservoir chamber 92 whichcould sometimes otherwise occur during a quick brake release when thefluid level in chamber 92 is low. The expansion of fluid in chamber 28under pressure when the brake is released can cause a squirt-like actionofthc fluid through compensation port 54 with sufficient velocity tocarry some of the fluid out of the secondary reservoir chamber 36 andinto the primary reservoir chamber 92. If the brake circuit connectedwith pressurizing chamber had suffered a loss of p essure. this pumpingaction could contribute to pumping fluid from pressurizing chamber 28 soas to unnecessarily deplete the brake circuit connected with thatchamber. By providing a baffle arrangement. this action is effectivelyprevented.

As is disclosed in the earlier filed patent application referred toabove. a single fluid level sensor ll0 may be provided in the primaryreservoir chamber 92 and this sensor is used to detect the loss of fluidin either brake system. When the fluid level in chamber 92 falls belowthe level of sensor 0. whether from pressure loss or excessive brakelining wear. in either or both of the brake circuits served by themaster cylinder. the sensor energizes a warning circuit. The singlesensor simplifies the arrangement and results in a more economicalassembly than is the case when separate sensors must be used for eachbrake circuit reservoir.

What is claimed is:

l. A master cylinder reservoir arrangement comprising:

a master cylinder body having a first fluid reservoir chamber formedtherein with an open top. a bottom provided with a compensation port.and a cylindrical side wall having an internally threaded sectionadjacent the open top;

a main fluid reservoir body defining a second fluid reservoir chamberhaving a side wall and a removable sealing top and a bottom. said bottomhaving an aperture therein positioned over said first fluid reservoirchamber and being at least as large as said first fluid reservoirchamber open top.

and means securing said main fluid reservoir body to said mastercylinder body comprising a tubular member having an externally threadedsection and a centrally apertured head section of greater diameter thansaid externally threaded section to provide a shoulder therebetween anda centrally apertured cap. said externally threaded section extendingthrough said aperture and threaded into said internally threaded sectionof said first fluid reservoir chamber cylindrical side wall with saidshoulder tightly engaging said second fluid reservoir chamber bottom toretain said main fluid reservoir body on said master cylinder body. saidhead section having a baffle plate adjacent thereto and mounted withinthe upper portion of said tubular member. said baffle plate having aplurality of apertures adjacent the outer periphery thereof and a solidcenter section in axial alignment with the aperture of said cap. saidplurality of apertures being also positioned adjacent the inner wall ofsaid tubular member externally threaded section to provide a tortuousfluid flow path between said second fluid reservoir chamber and saidcompensation port.

2. In a master cylinder assembly having a master cylinder body and afluid reservoir body. said master cylinder body having a bore therein.first and second pressurizing pistons reciprocably received in said boreand defining therewith first and second fluid pressurizing chambers:

first and second secondary fluid reservoir chambers formed in saidmaster cylinder body each having an open top and an internally threadedside wall and a bottom provided with compensation port means connectingwith said bore:

a primary fluid reservoir provided by said fluid reservoir body andhaving first and second apertures in the bottom thereof aligned withsaid first and second fluid reservoir chambers;

first and second externally threaded securing means having fluidpassages therethrough and shoulders thereon and respectively extendingthrough said apertures and threaded into said first and second secondaryfluid reservoir chambers with said shoulders tightly engaging the bottomof said primary fluid reservoir to hold said fluid reservoir body onsaid master cylinder body.

said first securing means having a circumferentially apertured bafflemounted in said fluid passage thereof and a center apertured top portionpositioning said baffle in the upper end of said fluid passage with thebaffle and top portion apertures being out of direct alignment with eachother and the apertures of said baffle being out of direct alignmentwith said compensation port means to prevent a direct line of fluid flowbetween said compensation port means and said primary fluid reservoirand thereby prevent a squirt-like return of fluid from said first fluidpressurizing chamber directly into said primary fluid reservoir uponbrake release.

1. A master cylinder reservoir arrangement comprising: a master cylinderbody having a first fluid reservoir chamber formed therein with an opentop, a bottom provided with a compensation port, and a cylindrical sidewall having an internally threaded section adjacent the open top; a mainfluid reservoir body defining a second fluid reservoir chamber having aside wall and a removable sealing top and a bottom, said bottom havingan aperture therein positioned over said first fluid reservoir chamberand being at least as large as said first fluid reservoir chamber opentop; and means securing said main fluid reservoir body to said mastercylinder body comprising a tubular member having an externally threadedsection and a centrally apertured head section of greater diameter thansaid externally threaded section to provide a shoulder therebetween anda centrally apertured cap, said externally threaded section extendingthrough said aperture and threaded into said internally threaded sectionof said first fluid reservoir chamber cylindrical side wall with saidshoulder tightly engaging said second fluid reservoir chamber bottom toretain said main fluid reservoir body on said master cylinder body, saidhead section having a baffle plate adjacent thereto and mounted withinthe upper portion of said tubular member, said baffle plate having aplurality of apertures adjacent the outer periphery thereof and a solidcenter section in axial alignment with the aperture of said cap, saidplurality of apertures being also positioned adjacent the inner wall ofsaid tubular member externally threaded section to provide a tortuousfluid flow path between said second fluid reservoir chamber and saidcompensation port.
 2. In a master cylinder assembly having a mastercylinder body and a fluid reservoir body, said master cylinder bodyhaving a bore therein, first and second pressurizing pistonsreciprocably received in said bore and defining therewith first andsecond fluid pressurizing chambers; first and second secondary fluidreservoir chambers formed in said master cylinder body each having anopen top and an internally threaded side wall and a bottom provided withcompensation port means connecting with said bore; a primary fluidreservoir provided by said fluid reservoir body and having first andsecond apertures in the bottom thereof aligned with said first andsecond fluid reservoir chambers; first and second externally threadedsecuring means having fluid passages therethrough and shoulders thereonand respectively extending through said apertures and threaded into saidfirst and second secondary fluid reservoir chambers with said shoulderstightly engaging the bottom of said primary fluid reservoir to hold saidfluid reservoir body on said master cylinder body; said first securingmeans having a circumferentially apertured baffle mounted in said fluidpassage thereof and a center apertured top portion positioning saidbaffle in the upper end of said fluid passage with the baffle and topportion apertures being out of direct alignment with each other and theapertures of said baffle being out of direct alignment with saidcompensation port means to prevent a direct line of fluid flow betweensaid compensation port means and said primary fluid reservoir andthereby prevent a squirt-like return of fluid from said first fluidpressurizing chamber directly into said primary fluid reservoir uponbrake release.